Iron core inductance



NOV. 11, 1941. in- 2,262,630

IRON CORE INDUCTANCE Filed June 23, 1959 OCT/W619 V0474 am ur INVENTORIVEQBEET E/JE/MM/G ATTORNEY Patented Nov. 11, 1941 Herbert Bahring,Berlin-Kl. Machnow, Germany,

assignor to Fernseh Aktiengesellschaft, Berlin- Zehlendorf, GermanyApplication June 23, 1939, Serial No. 280,804 In Germany June 27, 1938 8Claims.

My invention relates to inductive systems with iron cores, through whichnon-sinusoidal currents are caused to flow, and particularly to a meansfor decreasing the voltage insulation problems encountered therein.

Inasmuch as my invention is particularly applicable'to oscillatorcircuits, including an iron core transformer, for generation of sawtoothcurrents and derivation of a D. C. voltage therefrom, the inventionshall be described in connection therewith, bearing in mind that it isin no way limited to such application alone. U. S. Patent 2,051,372,issued August 18, 1936, to Philo T. Farnsworth, and U. S. Patent2,059,683, issued November 3, 1936, to Philo T. Farnsworth, describe anoscillator circuit including an electron discharge tube and transformerfor generation of a sawtooth current flow in an inductive load. Thefirst-named patent also describes a method of producing a D. C. voltagederived from said sawtooth currents by rectification of a portion of thesawtooth current. Furthermore, co-pending U. S. application, Serial No.254,593, filed February 4, 1939, by Rolf Moller and Herbert Bahringunder the title, Sawtooth wave generator, Patent No. 2,218,764 grantedOctober 22, 19 0, discloses a means and method of deriving the filamentheating power for a rectifier tube, serving to produce the high D. C.voltage, by means of an auxiliary winding on the aforesaid transformerin the oscillator circuit.

Such circuits include an electron discharge tube having at least acathode, a control grid and a plate, whereby the primary winding of atransformer with an iron core is connected in the plate circuit, whilethe secondary winding is connected in the grid circuit. The sawtoothcurrents produced by such a circuit have a rapid rate of change in onedirection and a slow rate of change in the other direction, and thecorresponding voltages are alternately high and low. U. S. Patent2,051,372 shows a method and means for rectifying the so produced highvoltages preferably by means of a diode. The magnitude of the generatedhigh voltage is inversely proportional to the time of decay of thesawtooth wave, which in the television art is also commonly referred toas the retrace time. The retrace time in turn decreases with decreasingdistributed capacity of the inductive load as well as the transformerwindings. This leads to the development of low capacity windings for thetransformer. At high voltages this necessitates that the window oftheiron core and, therefore, the iron core itself, must be made large inorder to prevent arcing over if the iron core is grounded as usual. Thismeasure, however, reacts unfavorably upon the length of the iron path,the inductance per turn, the distributed capacity of the coil, theweight of the iron, the iron losses and the influence of the load uponthe generated high voltage.

It is the object of this invention to overcome the aforesaiddiificulties; to provide a transformer requiring weaker insulation; toprovide a transformer requiring insulation for only onehalf the peakvoltage occurring; to provide a circuit for decreasing the insulationrequirements without afiecting the wave shape of the generated sawtoothcurrent. Other features and advantages of my invention will becomeevident from the following description.

Referring to the drawing:

Figs. 1a. and 1b and 2a and 2b aid the explanation of the operation;

While Fig. 3 shows a preferred embodiment of my invention.

Broadly considered, my invention provides for holding the iron core ofthe transformer carrying plate and grid windings at a steady potentialabove ground and preferably in the order of one-half the peak-to-peakvalue of the highest voltage produced by the transformer. For thispurpose, I prefer to connect the anode of a diode to the center point ofthe transformer winding across which the highest voltage is produced andto conductively connect the cathode of said diode to the iron core ofthe transformer.

The invention shall now be explained more in detail in connection withthe drawing. Fig. 1a shows a sawtooth current with a retrace interval awhich, it caused to flow through an inductance, will produce the voltageshown in Fig. 1b. This voltage wave shows peaks 2 occurring duringretrace time a. It may be seen that this voltage is not symmetricalabout the zero line 5 inasmuch as the negative amplitude b is much lessthan one-half of the peak-to-peak value B. Fig. 2a shows a sinusoidalcurrent which, when caused to flow through an inductance, will produce asinusoidal voltage as indicated in Fig. 2b, which is symmetrical aboutzero line 6, whereby the negative portion 0 is onehalf of thepeak-to-peak value C. Zero lines 5 and 6 may indicate ground potentialat which the iron core in the above-described transformers was heldaccording to usual practice. In accordance with this invention, however,the iron core is to be held at a steady potential above ground,indicated by dotted line 1 in Fig. 1b,

which is gained by dividing peak-to-peak value B into two equal parts.Thus, it may be seen that the potential difierence between inductanceand iron core is the same at maximum negative as well as maximumpositive amplitude, while in the case where the iron core was held atzero or ground potential the potential difference at the positivevoltage peaks was nearly twice as high. Fig. 21) indicates thatelevating the potential of the iron core above ground would be, uselessfor sinusoidal waves inasmuch as, in the same measure as the voltagedifference, betwee iron core and transformer winding would be decreasedfor the positive amplitudes, it would be increased for the negativeamplitudes. Thus, the usefulness of my invention in the case of voltagewaves which are not symmetrical about a zero line will be readilyevident.

Fig.3 shows an embodiment of my invention in combination with a knownmeans for gencrating a sawtooth current flow through aninductance, as isdescribed in the above-mentioned U. S. Patents 2,051,372 and 2,059,683,and copending U. S. application, Serial No. 254,593. In Fig. 3, 8 isan'oscillator tube possessing a cath-. ode, a control grid and an anode.9 is the transformer winding connected in the anode... circuit of 8,which is connected in series with a voltage step-up winding I0. LI is atransformerwindingconnected in the grid circuit of. tube. 8 in serieswith an inductive. load [3 and a parallel combination of resistanceZlandcon denser. 2|- The junction of windings Band lllis connected withthe anode of tube 8, while thefreeendof 9 is connectedto a terminal23towhich a posi: tive operating potentialv for. the anode. oi the tube 8 isapplied. The tree end. of voltage. step: up winding I0 is connectedtothe anode of diode IS, the cathode of whichisconnected to ground andterminal through..;smoo.thing..condenser. L8 The filamentary cathode of.IE. is also, connected to high voltage output'terminal L6- ascWQll. asto winding 25.. on the. transformer. Which supplies the filamentheatingpower for, [S It maybe understood. that the filament heating power for;IS mayalso be derived from. ahd ticrenh ouxcc Th .v v lta e p aks.appear ng acrp s e... tr m: former. wi dings hand L0.a elcqtiiisd.bycgle lns or, the, diode. l5, and ahiehn; g tputvoltaet ieveloped etw e het rmi lals. fir ntl- U.- The ombinat on, of w ndi s. 9.and I 0.; isdivided nt equ l. arts y. e ter, tan, &5 with. $2 1. nectedht eanode o a. diqdc. I Namath.- .o... e..i.r ore by means a 4.- Thefieg entary a t e de. bf 3. is c n e te withtransiermer Wind n 4.. by meanof w c h filament heat n P wer is er ed fr m he r esferme ay; e nd r tot a hafihmeetheeiina owe we d ed m lit et eur t i a balancing ,liqteltiemete n. the. e tiede Jt Q iP bet.

n erati n. t w th er n e er causedjto flo'w, through inductive load I9;which maybe a stator scanning coils. associated with a" cathode:rayltube. The freq'u' 'icy' of. the saw; tooth cur nt waves is determned by. the i tiine constant; of thetsmemmmi bf. and "2]. voltagewill'be produced."across, the sei ies combina'tionfof windings HI and.H] which. hasth' wave" shape indicated in Fig. 1 b; This volt age isrectifie'dby' means of diodeili andpan. be used to sunny the .anodeof acathode ray... tube with high. voltage," Diode. law-i111 in the,'s ameanner produce. "a' high DL f Q. voltage; however} of only half magnitudeof that produced by diode l5 because its anode is connected to thecenter tap of windings 9 and HI. This voltage is applied through lead l4to the transformer core l2 and keeps the latter at a steady potentialpositive in respect to ground by substantially one-half the positivevoltage pea-lg. It may be understood ot course, that the iron core mustnow also be insulated against parts at ground potential for one-half thehigh voltage produced by rectifier l5.

If the invention is to be used in combination with the above-describedrelaxation oscillator and rectif er for generation of high voltage, itis necessary." to. prevent the voltage between the transformer windingsand the core from rising to a value greater than substantially one-halfthe high. voltage when putting the device into operation. For thispurpose, the time constant resulting from the combination of thecapacity of, the. transformer core. and. the inner resistance of diode1,3.- in non-conductive. condition. is. pref: erablx made equal; to. orsmaller than. the. time. constan esulting rom. the. apacity. ofv smooth:ing condenser l8 and the interior resistance of. gh vol age diode t5...In this manner the potential. 2 cores t is brought. to. one-halt the hvolta e. e ore he enerated high vo ta e as reached its. stat onary vaue- -hai'e escribed my. nv ntion. ons nect en wi h. emi r tion sc latorused; to pro: due s wtoot cur ents, n. an, ind tive. deflect: 1 a e. andtopr siu e a high .2.. .0; voltage by it eel a ireefqeia Q1? v irz' eeew t t 9133 ndu ta ce- We la its l rleae e i eti: ale 'e eee elt se eutu ll i i e $3.59 the Ofth'an to thejlothenj andgrnean s for maintain;

ing said core at a; substa tially ste dygpotential with respect, to.saidzero pptntialflin of' th same polarity as said. excursions. of:greater. ampl lldefoi said voltaglwav. Y i

2. In combinationfaninductance element hav ing an iron core. meansforfcaiusingfa noiis sinusoidal alternating. current tobfiowj. throughsaid inductance element, andv producing. voltage pealrs across saidductanceQelemi it; mea'nsirdr rectifying a portion, of, saidf'voltagepeaks. and means for; applying said rectified .;.voltag.,e.lto; s idIIVOIIVCQIZBT v 1 L 3. In. combination, an induptive winding have ingenter. apart. irjqn qn -meen fm ausin al snrs n qis al er flowh ou h. Sid.- 31 m nmdu j vo e ks egre s. ai W 2; gel a di de bar ai nod nd,@CePhQ aW QIiSQ OI. C Qhecti esaid ent tmoea em d me n f pr e inectingsaidcathodetosa diron core; it v I i 4. In; combination arelaxation; oscillator inr eluding an electron discharge-tube havingalcathlode, a [condor rit; and an, anodegandr nfccr ran i m e tessin lvr nd 'i' st ne .ori'said win iest b n n ectedm. node; circuit etsa sltbehe thet tteii, m i i sshin connected in the grid circuit of saidtube, means for supplying D. C. operating potentials to said anode andsaid cathode and means for maintaining said iron core at a steadypotential of a value intermediate said operating potentials of saidanode and said cathode.

5. In combination, a relaxation oscillator including an electrondischarge tube having a cathode, a control grid and an anode, an ironcore transformer possessing two windings, one of said windings beingconnected in the anode circuit of said tube, the other of said windingsbeing connected in the grid circuit of said tube, and means formaintaining said iron core at a steady potential above ground bysubstantially one-half of the peak-to-peak value of the A. C. voltagegenerated by said oscillator.

6. In combination, a relaxation oscillator including an electrondischarge tube having a cathode, a control grid and an anode, an ironcore transformer possessing two windings, one of said windings beingconnected in the anode circuit of said tube, the other of said windingsbeing connected in the grid circuit of said tube, said anode windinghaving a center tap, and a diode having an anode and a cathode, meansfor connecting the anode of said diode to said center tap, and means forconnecting the cathode of said diode to said iron core.

7. In combination, a relaxation oscillator including an electrondischarge tube having a cathode, a control grid and an anode, an ironcore transformer carrying a first winding connected in the anode circuitof said tube, a second winding for voltage step-up in series with saidfirst winding, and a third winding connected in the grid circuit of saidtube, a center tap dividing the series combination of said first andsaid second windings into equal parts, and a diode having an anode and acathode, means for connecting the anode of said diode to said center tapand means for connecting the cathode of said diode to said iron core.

8. In combination, an inductance element having an iron core, means forcausing a flow of non-sinusoidal alternating current through saidinductance element to produce a voltage wave across said element, saidwave being unsymmettrical about a zero potential line and havingexcursions of greater amplitude to one side thereof than to the other,and means for maintaining said core at a substantially steady potentialwith respect to said zero potential line of such magnitude and polaritythat the excursions of said voltage wave to either side of lastnamedpotential are of equal amplitude.

HERBERT BAHRING.

